Are IMR Reloading tables trustable ?

30 May 2005, 22:06

Just happened to finish reloading and testing my first batch of 45/70 cartridges ...

Hornady 300 gr HP with 53 grains of IMR3031 to be shot from a MArlin 1895SS ...

Accuracy is outstanding (using an IOR 4x32), but my concern started when measuring its speed ...
I have an Oehler chronograph (rather used or better say bad used !) which make me doubt about its performance ...

The fact is that for that reload, IMR states I should be achieving something around 1900fps, but my chronograph "said" it was only 1650 ...

Powder in excellent conditions, and no, I donÂ´t have any other chronograph available !!

BTW, no signs of over pressure at this stage ...

Comments ?? I donÂ´t want to stress too much the brasses, since in my country they are quite difficult to find nowadays ... but will like to achieve a velocity of 1900/1950 fps .... Hogs are waiting for this combo

!!

regards

30 May 2005, 22:36

delloro

The IMR data was very close for me with 51.9 gr. of 3031 and the Rem 405 sp for 1800 fps in my 1895SS.

Check your chronograph against a known factory load and see if it is correct.

30 May 2005, 22:55

Afrikaander

quote:
Originally posted by delloro:
The IMR data was very close for me with 51.9 gr. of 3031 and the Rem 405 sp for 1800 fps in my 1895SS.

Check your chronograph against a known factory load and see if it is correct.

Then, a lighter bullet with a hotter charge MUST go faster than yours 1800 fps .... thanks Delloro !!

Next full moon is when the ultimate test will take place

!

Regards

30 May 2005, 23:09

denton

Most reloading data are developed in a pressure barrel, which is cut to minimum specifications. This will produce higher pressures and higher bullet speeds than an "average" or middle of spec chamber and barrel.

Some of the data are developed in ordinary rifles. You have to watch.

30 May 2005, 23:22

johnch

I just looked at a Hornady book and they list for 45/70 with 300 gr HP
40.9 gr of IMR 3031 = 1300 fps as min
52.4 gr of IMR 3031 = 1700 fps
54.7 gr of IMR 3031 = 1800 fps
56.9 gr of IMR 3031 = 1900 fps as max

1650 fps is about 100 fps slower than I would have expected .
Maybe you have a slow barrel ?
Different books list different loads.

Johnch

30 May 2005, 23:32

Afrikaander

I dont have the Hornady manual, thanks for that info, Johnch !

Looking at it, it seems that I should look for a hotter charge, something around 55 grains of 3031 ...

BTW, my barrel has a micro groove rifling, being 22Â´long ...

Regards,
Martin

31 May 2005, 08:39

delloro

quote:
BTW, my barrel has a micro groove rifling, being 22Â´long ...

Regards,
Martin

Mine, too.

31 May 2005, 18:47

El Deguello

quote:
Originally posted by Afrikaander:
Just happened to finish reloading and testing my first batch of 45/70 cartridges ...

Hornady 300 gr HP with 53 grains of IMR3031 to be shot from a MArlin 1895SS ...

Accuracy is outstanding (using an IOR 4x32), but my concern started when measuring its speed ...
I have an Oehler chronograph (rather used or better say bad used !) which make me doubt about its performance ...

The fact is that for that reload, IMR states I should be achieving something around 1900fps, but my chronograph "said" it was only 1650 ...

Powder in excellent conditions, and no, I donÂ´t have any other chronograph available !!

BTW, no signs of over pressure at this stage ...

Comments ?? I donÂ´t want to stress too much the brasses, since in my country they are quite difficult to find nowadays ... but will like to achieve a velocity of 1900/1950 fps .... Hogs are waiting for this combo !!

regards

Your chronograph is probably telling you the truth! All rifles are individuals, so yours may not produce as high a velocity as some others with the same bullets and powder charge. I personally use 53 grains of IMR 3031 with 400-405 grain bullets in my .45/70, so it is not too much of a problem for you to increase your powder charge of 3031 with that lightweight 300 grain bullet.

I have seen one published maximum load for the Marlin '95 that used 58 grains of IMR 3031 with the Hornady 300 grain bullet, that gave 2000 FPS MV. Of course, since it is close to a true max load for the Marlin, work up slowly!

I use 60 grains of RE 7 with a 400-grain Barnes Original semi-spitzer in my .45/70 Ruger No. 1, and get 2270 FPS MV and 1.5 MOA accuracy - but the recoil is brutal! Such a load would be way over max. in a Marlin, or ANY rifle except the Ruger!